This invention relates to direct dyes having a quaternary center with a long aliphatic chain, compositions comprising those dyes, and a process for using those compositions to dye hair.
Direct or semipermanent dyes are very widely used in the field of hair coloring. However, conventional direct dyes have a low affinity for hair and are not very shampoo stable.
Direct dyes having a quaternized amino group are also known. For example, U.S. Pat. No. 3,560,136 (Kalopissis et al.) and U.S. Pat. No. 4,018,556 (Kalopissis et al.) describe compounds of the formula: ##STR1## in which R', R" and R'" are C.sub.1-4 alkyl; and R.sup.1 and R.sup.2 are each, independently, hydrogen, lower alkyl, C.sub.1-6 lower hydroxyalkyl, or like substituents.
GB 1,164,824 (Kalopissis et al.) and U.S. Pat. No. 3,978,061 (Kalopissis et al.) describe the above compounds wherein the NR.sup.1 R.sup.2 group is in the meta-position to the nitro group.
These direct dyes having a quaternary center have a somewhat higher affinity for hair than conventional direct dyes. However, direct dyes having a quaternary center have different affinities for newly grown virgin hair near the root of the hair shaft and for slightly to severely damaged hair along the lower parts of the hair shaft. This hair affinity difference results in aesthetically undesirable uneven dyeing.
Surprisingly, applicants have found that direct dyes having a quaternary center with a long aliphatic chain have a higher affinity for hair and are more shampoo stable than conventional direct dyes, and produce pleasing uniform dyeing that cannot be achieved with direct dyes having just a quaternary center.